
#! /bin/bash
trap 'echo "before execute line:$LINENO, a=$a,b=$b,c=$c"' DEBUG
a=1
if [ "$a" -eq 1 ]
then
    b=2
else
    b=1
fi
c=3

echo "end"

# before execute line:4, a=,b=,c=
# before execute line:5, a=1,b=,c=
# before execute line:7, a=1,b=,c=
# before execute line:11, a=1,b=2,c=
# before execute line:13, a=1,b=2,c=3
# end